1. Field of the Invention
This invention pertains to boats and ships having planing hulls. More particularly, it pertains to V-bottom planing hulls having stabilizing recesses along their bottom surfaces which produce enhanced planing performance and improved stability in turns, among other benefits.
2. Review of the Prior Art
High speed motorboat hulls (such as are used for water skiing and racing) are increasingly of one or the other of two general planing types, namely, shallow V-bottom hullforms and tunnel hullforms. In a planing hull, the objective is to drive the hull across the surface of the water; the weight of the hull is supported by dynamic (motion-induced) forces applied to the hull by the water, not by buoyant forces due to immersion of the hull in the water. When a shallow V-bottom planing hull moves at high speed, the dynamic support forces act on a very small area of the hull along its centerline at its rear end; all other portions of the hull are out of the water. When a tunnel-type planing hull moves at high speed, the dynamic support forces act on small areas of the hull adjacent its rear end but spaced on opposite sides of the centerline.
V-bottom boats are much more popular than tunnel-hull boats for general use, water skiing and racing. Because of the different way that planing forces act on tunnel-hull boats, they have a much different "helm" (feel of the steering controls) than V-bottom boats at high speeds, and more skill and experience is required to operate a tunnel-hull boat at high speed than is the case with V-bottom hulls. However, tunnel-hull boats are considered safer at high speeds, if driven by a skilled operator, than V-bottom boats. A V-bottom boat turns more normally at high speed than a tunnel-hull boat; it tips more into the direction of the turn. On the other hand, a V-bottom boat tends to bounce substantially at high speed, regardless of the state of the water over which it moves. V-bottom boats are much more sensitive to chop of the water surface, and at high speeds they tend to fall off the center point of the V on which they are supported by the dynamic planing forces. In a turn at high speeds, a V-bottom boat slides or slips laterally, and thus makes a wide rather than a tight turn; this is a distinct disadvantage in racing. A tunnel-hull boat has better high speed performance characteristics than a V-bottom boat. A skilled operator would prefer a tunnel-hull boat over a V-bottom boat. But the great majority of boat owners do not desire very high performance and do not have the skill to safely operate a tunnel-hull boat.
My prior U.S. Pat. No. 3,653,609 describes, principally in the context of aircraft, a substantially cylindrical lifting surface arrangement in which the surface is downwardly-open and concave, and is aligned with the direction of flight and open at its forward and rear ends. The surface is essentially free of camber along its length. As it moves through the air with a small angle of attack, air engages the surface. The surface has side edges, aligned with the length thereof, which extend downwardly relative to the middle of the surface. For example, if as preferred the surface has a semi-round arcuate transverse configuration, the side edges are disposed below the highest point of the arc a distance which is substantially equal to the radius of the arc so that the margins of the surface adjacent the side edges are substantially vertical. Air engaging the concave surface as it moves forward is kept in contact with the surface; the side edges of the surface prevent substantial lateral spill of air out of the concavity defined by the surface, so that substantially all of the air which enters the front end of the concavity leaves the vicinity of the surface through the open rear end of the concavity.
My prior U.S. Pat. No. 3,791,329 describes a boat, generally of the tunnel-hull type, in which two semi-cylindrical lifting surfaces, generally in accord with the teachings of U.S. Pat. No. 3,653,609, are provided, one along each side edge of the hull. U.S. Pat. No. 3,791,329 teaches that the lifting surfaces are located below all other downwardly facing hull surfaces, and so the hull surface between the lifting surfaces is located above the lifting surfaces.
When a hull of the type shown in U.S. Pat. No. 3,791,329 is propelled through the water, the lifting surfaces become effective, at surprisingly low speeds, to develop sufficient lift to raise the hull in the water until essentially only the lifting surfaces contact the water. Thereafter, the hull is supported on only the lifting surfaces at the water surface. The lifting surfaces cooperate with the water surface and do not rely upon submergence in the water as is the case with hydrofoils, but neither do the lifting surfaces function in a manner closely akin to water skis. They operate to produce lift but without the need for submergence. The tunnel-type hull, when driven at speeds substantially greater than the speed at which the lifting surfaces act to cause the hull to step out of the water onto the water surface, creates essentially no wake; the hull, in effect rides on two rails of water created by the lifting surfaces on the ambient water surface. The hull is therefore very fast and remarkably insensitive to chop on the surface of the water over which it moves. A need exists for similar improvements in V-bottom hulls which, as noted, are considerably more popular than tunnel-hulls.